Identification of Methane Emissions in an Urban Setting ESRL Global Monitoring Annual Meeting May17-18, 2011
Collaborators in this effort • Nathan Phillips & Lucy Hutyra – Boston University • Jocelyn Turnbull & Colm Sweeney – NOAA/ESRL • Paul Shepson & Maria Obiminda Cambaliza – Purdue • Eric Crosson, Chris Rella, & Sze Tan – Picarro, Inc. • Robert Ackley – Gas Safety, Inc.
Objectives of this effort • As an extension of the INFLUX work – Identify methane source locations and gather information on methane flux signals (relative magnitudes). • Provide prior knowledge for inversion models. • Data to help validate inversion model results. • Information to help improve flux measurements from aircraft. • Data could help to model cross-wind dispersion in an urban environment.
Method: Measuring Methane Plumes to Determine Source Locations • Map out methane concentrations Wind while driving along roads and highways. – CH 4 : 2 ppb precision at 0.5 Hz. Methane – GPS data Source – Wind velocity methane plume
Method: Identifying methane source locations Guidance from Simple Gaussian Plume Model Sources Reconstruction Source locations calculate from plumes roads Four source locations o in 20 o steps methane source and plume Winds: 0 to 360 Atmospheric stability class C
Model Results: Winds from only two orthogonal directions…….source location looks possible. Sources Reconstruction Atmospheric Stability Class F Class A
From Models to Reality: Measurements in Indianapolis 40 PlumeRUN1-4_19_2011-Data-landfill Methane Measurements Taken While Driving Methane measurements while driving through plume 35 Methane Concentration (parts per million) 30 Methane (ppm) 25 20 15 10 5 108.560 108.561 108.562 108.563 108.564 Distance Traveled
“Methane Maps” of Indianapolis Wind direction, 23km/hr 5 4 3 2 1
Some Sources are easy to Identify 5 4 3 2 > 25 ppm 1
Others are NOT so Easy 5 4 3 2 1
Methane Data Taken the Next Day 5 Wind direction, 23km/hr 6 7 4 8 3 2 1
Reproducibility of Plume Measurements Repeated landfill plume measurements taken while driving 2 km from source. (Location: Danville, IN) - Wind speed = 3.8 ± 1.2 km/hr - Source Flux ≅ 7,000 grams / minute 1.5 km 45 minutes High variability in plume shape. Take advantage by……
Stationary Tracer Method to Assess Fluxes Wind acetylene Landfill methane plume tracer plume methane • Fixed location 1300 m downwind of landfill • Natural variation in wind direction & wind speed will cause variability in signal as the plumes sweep across the detection point • High correlation indicates good overlap between plumes
Methane Flux Determination (Location: Danville, IN) • Plot methane vs. acetylene. • Slope of line gives ratio of emission rates. = 7.5 moles / s
A Very Complex Methane Map: Boston Play Video
Natural Gas Leaks in and around Boston
Natural Gas Leaks Destroying Vegetation • Leaks in aging natural gas pipelines are killing trees all across the northeast. – Natural gas leaks can kill trees by displacing oxygen in the soil and drying out their roots. – 7,500 to 10,000 trees affected in Boston area alone. • Several cities are asking for damages in excess of $1M each. Flux (cubic feet / m 2 -day) Gas in air 8” below at surface surface 0.237 26% 1.407 48% 1.007 80% 0.012 63% http://natgaspollutes.com
Summary • Identification of methane source locations by driving around looks possible. • Flasks need to be analyzed. • Need model to reconstruct methane probability distribution from plume data. • Need to take more systematic data.
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